The invention relates to a header for a flat tube liquefier disclosed, for example, in German Utility Model Patent G 90 15 090.2. This header is based on the object of having the exterior width dimension of the header exceed as little as possible the length dimension of the cross section of the flat tubes to be inserted into the header. For this purpose, the first component which is provided with the tube bottom for the flat tubes is surrounded in a fork-like fashion by the second component, with it being possible to configure the outer arm of the respective fork-like enclosure with a relatively thin wall thickness. Compared to European published Patent Application EP-A2-0,374,896 --and comparable other prior art--the total depth of the liquefier comprising the header, the flat tubes and ribs thereon was reduced. In EP-A2-0,374,896, the first component is disposed on the inside and the second component on the outside in the two overlap zones between the first component and the second component, and the free edges of the second component are surrounded toward the exterior by the first component. A comparable arrangement of the first component, which is provided with the tube bottom, on the inside with respect to the second component that complements the header is also incorporated in other prior art structures in which the header is composed of two overlapping complemental components. Regarding the structural depth of the flat tube liquefier, a general construction difficulty has arisen in connection with such headers that are composed of two parts, for example, compared to European Patent EP-B1-0,255,313, Where the header is composed of a one-piece round tube and thus is not involved in any case with increases in the structural depth due to overlapping wall thicknesses. On the other hand, however, such an integral header has the drawback that it is not possible to widen the flat tubes from the interior of the header toward the receiving slots, which is desirable for reliable and secure soldering, and is even a prerequisite in practice for soldering under vacuum conditions. Another difficulty in the use of slotted integral tubes is that it is extremely difficult to subsequently properly produce receiving slots for flat tubes in these tubes. The practical realization of EP-B1 -0,255,313 now in existence therefore uses the expensive detour, which is difficult from a manufacturing aspect, of initially stamping the receiving slots into a still flat sheet metal and to then shape this metal sheet into a round tube and weld it at a sloping abutment edge. In contrast thereto, with headers that are assembled of two parts, to which the invention relates, it is possible to work without difficulty from the interior of the header toward the first component that forms the tube bottom, also to stamp out the receiving slots for the flat tubes, and to then tightly seal the header with the second component. However, the stamping out of the receiving slots may also be effected when the sheet metal is still in the flat state without it then being necessary to deform this sheet metal with the complicated butt welding process into a single tube as is the case in EP-B1-0,255,313.
In the header of EP-A2-0,374,896 as well as in the header of German Utility Model Patent G 90 15 090.2, the connection between the two components is realized by a fork-shaped pocket into which a wall of the other component is inserted. In the case of EP-A2-0,374,896, the sheet metal walls of both components are pressed together after they have been assembled. In the header according to German Utility Model Patent G 90 15 090.2 in which the complementing second component is an extruded profile, the insertion tolerances encountered are even closer right from the start, because a subsequent compression cannot be performed. It is here necessary to overcome difficulties during assembly not only because of the close available tolerances but also because of the interacting material roughnesses. In neither of the prior art headers according to EP-A2-0,374,896 or according to German Utility Model Patent G 90 15 090.2 is there a significant positive lock which secures the two components against sliding apart during the soldering process with a relaxation of the previously performed mechanical tensioning.